8 Manage Users and Groups

# 8.1 Create, delete and modify local user accounts

```
$ sudo useradd john
```
When the command is triggered :
- a user is created with a userid
- a group is created with the same uid and is made primary group
- a home folder is created
- a shell present at /bin/bash is assigned
- files present at /etc/skell are copied to the home directory

Default actions done when a new user is created can be found at:
```
$ useradd --defaults
or
$ useradd -D
```

To set a password
```
$ sudo passwd john
```

To delete an account
```
$ sudo userdel john
```

During user deletion, home directory can also be deleted
```
$ sudo userdel --remove john

$ sudo useradd --shell /bin/othershell --home-dir /home/otherdir john

$ sudo useradd -s /bin/othershell -d /home/otherdir john
```

You can specify a uid 
```
$ sudo useradd --uid 1100 smith
```

## Create a system account
```
$ sudo useradd --system sysacc
```

System accounts have __id < 1000__


To modify user details after creation
```
$ sudo usermod --home /homeotherdir --move-home john

$ sudo usermod -d /home/otherdir -m john
```

To change the username
```
$ sudo usermod --login jane john 
or
$ sudo usermod -l jane john
```

To change user shell
```
$ sudo usermod --shell /bin/othershell jane
or
$ sudo usermod -s /bin/othershell jane
```

To disable an account
```
$ sudo usermod --lock jane

$ sudo usermod --unlock jane
```

Set date for account expiry
```
$ sudo usermod --expiredate 2021-12-10 jane 
```

To remove and expiration date
```
$ sudo usermod --expiredate "" jane
```

Password expiration
```
$ sudo chage --lastday 0 jane

$ sudo chage -d 0 jane
```

unexpire the password
```
$ sudo chage --lastday -1 jane

$ sudo chage -d -1 jane
```

To set expiry every 30 days
```
$ sudo chage --maxdays 30 jane

$ sudo chage -M 30 jane
```

To set passwords that never expire
```
$ sudo chage --maxdays -1 jane

$ sudo chage -M -1 jane
```

To see when the account password expires
```
$ sudo chage --list jane

$ sudo chage -l jane
```


# 8.2 Local Groups and Group Memberships

To view groups a user is assigned to
```
$ groups john
```
Each user can belong to one or more groups

Primary group = login group
```
$ sudo useradd john

$ sudo groupadd developers
```
Add user to a group
```
$ sudo gpasswd --add john developers
$ sudo gpasswd --a john developers
```
To remove user from a group
```
$ sudo gpasswd --delete john developers
$ sudo gpasswd -d john developers
```
Change users primary or login group
```
$ sudo usermod --gid developers john
$ sudo usermod -g developers john

usermod -g changes secondary group
usermod -G changes primary group
```
To rename a group
```
$ sudo groupmod --new-name programmers developers
$ sudo groupmod -n programmers developers

To delete a group
$ sudo groupdel programmers
```


# 8.3 Manage access to the root account



# 8.4 Configure PAM

PAM related files are found in : /etc/pam.d/